The present invention relates to an ink jet head and a production method of the same.
In an ink jet head employed in ink jet printers, a method is available in which a pressure pulse is generated in the ink chamber employing a piezoelectric element, and thus ink droplets are ejected from the nozzle. In said piezoelectric element, an electrode, which applies driving voltage, is essential, and said electrode is arranged, being in direct contact with ink. When the electrode is brought into contact with a water based ink, water in the ink is subjected to electrolysis which generates bubbles, while the electrode is dissolved resulting in disconnection while running. Further, even when oil based ink is employed, carbon chains are formed from organic materials in the ink to cause short circuit. Accordingly, it is desired to protect the electrode from ink. In order to achieve this goal, it is known that various types of organic or inorganic layers are formed on the electrode.
Listed as such inorganic layers are various types of oxides and nitrides. For instance, included are silicon-oxygen (SiO), silicon-nitrogen (SiN), silicon-oxygen-nitrogen (SiON), silicon-carbon (SiC), aluminum-nitrogen (AlN), silicon-aluminum-nitrogen (SiAlN), aluminum-oxygen (AlO), aluminum-silicon-oxygen (AlSiO), and silicon-aluminum (SiAl).
Employed as organic layers are various types of polymer layers, and it is proposed to employ polyparaxylene as representative polymers.
When bubbles are mixed in an ink channel, especially in an ink chamber to which pressure is applied employing a piezoelectric element, said bubbles absorb applied pressure which decreases the speed of ejected ink or occasionally results in no ink ejection. Accordingly, in the ink jet head, it is required that the interior of the ink channel be smooth and continuous.
From the foregoing, the present invention has been achieved. It is a first object of the present invention to provide an ink jet head in which degradation of the electrode of said ink jet head is minimized. It is a second object of the present invention to provide an ink jet head comprising a layer on the electrode which is readily formed. It is a third object of the present invention to provide an ink jet head in which each member in said ink jet head is not degraded and a smooth and continuous layer, which covers the electrode, can be easily formed.
In order to solve the aforementioned problems, as well as to achieve the objects, the present invention has been embodied as described below.
(1-1) An ink-jet head, comprises:
an ink chamber in which ink is stored;
a piezoelectric element to jet the ink from the ink chamber;
an electrode to apply an electric voltage onto the piezoelectric element;
a layer provided on the electrode by an electrodeposition method, the layer subjected to a process to change a surface energy.
According to (1-1), since materials, which are deposited employing electrodeposition, generally have a functional group, it is possible to control properties of a layer by controlling the amount of said functional group or by selecting the materials used. Thus it is possible to form a desired layer with response to the characteristics of an ink jet head as well as the ink itself. Further, when a treatment is carried out to vary surface energy, it is possible to markedly enhance the wettability between the ink jet head and the ink.
Further, when a layer is formed employing an electrodeposition method (even when a protective layer is formed employing materials which are inherently hydrophilic), the surface energy increases while minimizing the solubility of said surface layer in the ink. However, this causes a problem with insufficient wettability of the ink. In order to overcome this problem, when a treatment to vary the surface energy is carried out, it is possible to increase the wettability for the ink.
(1-2) In the ink-jet head of (1-1), the process to change a surface energy is a process to increase the surface energy.
(1-3) In the ink-jet head of (1-1), the process to change a surface energy is an oxidizing process.
(1-4) In the ink-jet head of (1-3), the oxidizing process is a plasma process.
(1-5) In the ink-jet head of (1-1), the layer contains polyimide.
(1-6) In the ink-jet head of (1-1), a thickness of the layer is 0.1 xcexcm to 50 xcexcm.
(1-7) An ink-jet head, comprises:
an ink chamber in which ink is stored;
a piezoelectric element to jet the ink from the ink chamber;
an electrode to apply an electric voltage onto the piezoelectric element;
a layer provided on the electrode by an electrodeposition method, the layer containing polyimide.
According to (1-7), when a polyimide layer is formed by electrodepositing a polyimide precursor followed by heating the deposited layer at relatively,high temperature, there is the possibility that the piezoelectric element, having a lower heat resistance, is damaged. However, it is possible to overcome this problem as follows. When the polyimide itself is electrodeposited, it becomes unnecessary to heat the piezoelectric element to a relatively high temperature. Thus it is possible to employ a piezoelectric element having a lower heat resistance. Further, when heated to a relatively high temperature, the polyimide melts to a fluid and the polyimide layer is partially removed to form pinholes. As a result, insulation degradation tends to occur. However, when the polyimide is electrodeposited, no heating is required to a relatively high temperature. As a result, it is possible to minimize such problems.
(1-8) In the ink-jet head of (1-7), the polyimide is made from 3,5-diaminobenzoic acid.
(1-9) In the ink-jet head of (1-7), a thickness of the layer is 0.1 xcexcm to 50 xcexcm.
(1-10) An ink-jet head, comprises:
an ink chamber in which ink is stored;
a piezoelectric element to jet the ink from the ink chamber;
an electrode to apply an electric voltage onto the piezoelectric element;
a first layer provided on the electrode by an electrodeposition method, and
a second layer provided on the electrode.
(1-11) In the ink-jet head of (1-10), the second layer is an organic layer.
(1-12) In the ink-jet head of (1-11), the organic layer contains polyparaxylylene.
(1-13) In the ink-jet head of (1-10), the first layer contains polyimide.
(1-14) In the ink-jet head of (1-10), a thickness of the layer is 0.1 xcexcm to 50 xcexcm.
(1-15) In the ink-jet head of (1-10), a thickness of a composite layer of the first layer and the second layer is 0.1 xcexcm to 50 xcexcm
(1-16) An ink-jet head, comprises:
an ink chamber in which ink is stored;
a piezoelectric element to jet the ink from the ink chamber;
an electrode to apply an electric voltage onto the piezoelectric element;
a first layer containing polyimide provided on the electrode, and
a second layer being an organic layer provided on the electrode.
(1-17) In the ink-jet head of (1-16), a thickness of a composite layer of the first layer and the second layer is 0.1 xcexcm to 50 xcexcm.
(1-18) In the ink-jet head of (1-16), the organic layer contains polyparaxylylene.
According to (1-10) or (1-16), it is possible to realize an ink jet head having ink resistance as well as insulation properties.
(1-19) A method of manufacturing an ink-jet head, comprises:
a step of forming a layer by an electrodeposition method on an electrode to drive a piezoelectric element to jet an ink from an ink chamber, and
a step of applying a process to change a surface energy onto the layer.
(1-20) A method of manufacturing an ink-jet head, comprises:
a step of forming a layer containing polyimide by an electrodeposition method on an electrode to drive a piezoelectric element to jet an ink from an ink chamber.
(1-21) A method of manufacturing an ink-jet head, comprises:
a step of forming a first layer by an electrodeposition method on an electrode to drive a piezoelectric element to jet an ink from an ink chamber, and
a step of forming a second layer on the electrode.
(1-22) A method of manufacturing an ink-jet head, comprises:
a step of forming a first layer containing polyimide and a second layer being an organic layer on an electrode to drive a piezoelectric element to jet an ink from an ink chamber, wherein the first layer is formed by an electrodeposition method.
Further, the above object may be attained by the following preferable embodiments.
(2-1) In an ink jet head wherein a piezoelectric element is driven and pressure is applied to ink to eject said ink from a nozzle, an ink jet head comprising a polyimide layer which covers the electrode which applies voltage to said piezoelectric element.
According to the invention described in (1) above, by comprising the polyimide layer which covers the electrode which applies voltage to the piezoelectric element, it is possible to protect said electrode from the corrosive action of the ink and to minimize the degradation of each member. In addition, said polyimide layer exhibits high critical surface tension as well as high wettability to ink. Thus, it is possible to obtain stable ejection.
(2-2) The ink jet head described in (2-1), comprising said poyimide layer as well as an organic layer in a multilayer form.
According to the invention described in (2-2) above, by applying said polyimide layer as well as said organic layer in a multilayer form, it is possible to more efficiently protect an electrode from ink and to minimize the degradation of each member.
(2-3) The ink jet head described in (2-1), wherein the thickness of said polyimide layer is in the range of 0.1 to 50 xcexcm.
According to the invention described in (2-3) above, a smooth layer is obtained; no pinholes are formed; no pressure loss occurs due to the deformation of a member, which applies pressure to ink, employing the layer thickness; and it is thereby possible to carry out excellent ink ejection.
(2-4) The ink jet head described in (2-1), wherein the thickness of said polyimide layer and said organic layer in a multilayer form is in the range of 0.1 to 50 xcexcm.
According to the invention described in (2-4) above, a smooth layer thickness is obtained; no pinholes are formed; no pressure loss results due to the deformation of a member, which applies pressure to ink, employing the layer thickness; and it is thereby possible to carry out excellent ink ejection.
Particularly, when a layer comprised of polyimide is provided on a layer comprised of polyparaxylylene, a palylene layer, which tends to form pinholes, is formed in advance, and the upper layer is comprised of polyimide. Thus wettability is enhanced and more stable ejection is possible.
(2-5) In an production method of an ink jet head in which a piezoelectric element is activated to eject ink, a production method of an ink jet head characterized in that a polyimide layer is provided which covers an electrode which applies voltage to said piezoelectric element.
According to the invention described in (2-5) above, it is possible to protect said electrode from the corrosive action of the ink; employing a simple configuration in which a polyimide layer, which covers said electrode, is provided. Further, it is possible to obtain an ink jet head in none of members are degraded, one which exhibits high critical surface tension as well as high wettability, and which results in stable ejection.
(2-6) The production method of an ink jet head described in (2-5), wherein said polyimide layer is provided on said electrode, employing an electrodeposition method.
According to the invention described in (2-6) above, it is possible to provide a polyimide layer which covers an electrode, by operating at normal pressure a unit comprised of an electrodeposition tank having dimensions similar to an ink jet head currently under production, and a small-scaled direct current source. Further, generally, own layer thickness control properties are exhibited in which the rate of electrodeposition decreases rapidly as electrodeposited thickness increases. However, by forming a layer employing an electrodeposition method in which an exposed electrode in an ink channel is used as the electrodeposition electrode, it is possible to readily form a smooth and continuous layer which covers said electrode. Further, compared to the conventional layer formation employing an electrodeposition method, which uses polyamide acids, a process is not required in which heating is carried out at relatively high temperature, and thus none of members in said ink jet head are degraded.
(2-7) The production method of an ink jet head described in (2-5) or (2-6), wherein said poyimide layer as well as said organic layer are provided in multilayer.
According to the invention described in (2-7) above, by providing a polyimide layer as well as an organic layer in a multilayer form, it is possible to more preferentially protect electrodes from the corrosive action of the ink to minimize the degradation of all members.